You're right- I've come across those M400 at convenience stores and don't recall any difficulties.

Was at a newly constructed BP corporate operated Arco last week and somehow they had MX915s deployed, they appeared brand new.

The system being used at Save Mart and Raleys is identical to the photo you have. Sprouts has the M400 at one store in my area but still has the old MX915s at the others; I haven't had any issues on their M400- it picks up the tap strongly on the first attempt.